The present invention relates generally to internal combustion engines for automotive vehicles, and more specifically, to an automotive vehicle having a motor/generator coupled to the engine. Further, the present invention relates, in particular, to a method for determining that the engine is producing torque in a hybrid electric vehicle.
Hybrid electric vehicles (xe2x80x9cHEVsxe2x80x9d) utilize both an internal combustion engine and one or more electric machines (e.g., motors/generators) to generate power and torque. The electric motor/generator within a hybrid electric vehicle provides the vehicle with additional degrees of freedom in delivering the driver-demanded wheel torque and may also be used to control the speed of the engine.
In one type of hybrid electric vehicle, commonly referred to as a xe2x80x9cpower splitxe2x80x9d configuration, the electric generator and the internal combustion engine are interconnected by use of a planetary gear set, and the electric generator selectively provides a reaction torque which may be used to control the speed of the engine.
During initial startup of the vehicle, the motor/generator functions as a starter. While functioning as a starter, the motor/generator provides a sufficient amount of starting torque to rotate the crankshaft of the engine before the cylinders are fired. After the engine is fired, an amount of engine torque is provided to the crankshaft from the combustion process in the cylinders. Once the engine is running, the motor/generator functions as a generator in which electric power is generated by the output rotation of the engine. This power is then used to charge the electrical system of the vehicle including an energy storage device which, in turn, is used to drive a traction motor.
In foreseeable automotive applications, the engine may be shut down during vehicle stops or other operating conditions. Thus, many startups could occur over the course of a trip. In such applications, the vehicle system controller requires a reliable indication that the engine has started and is running before making torque requests of the engine controller.
It is therefore an object of the invention to provide an improved hybrid electric vehicle system. It is another object to provide a reliable engine running indicator before torque requests are made of the engine.
In one aspect of the invention, a method of determining an operating state of an internal combustion engine in a hybrid electric vehicle drive system is provided. The HEV system comprises an internal combustion engine coupled to a generator. The engine includes fuel injectors responsive to a fuel command. The method comprises the steps of determining an ON/OFF status of the fuel command and determining the generator torque. The generator torque provides an indication of the actual engine torque. An engine running flag is set ON when the fuel command is ON and the generator torque value is above a predetermined value. Otherwise, the engine running flag is set OFF.
In a further aspect of the invention, the actual engine torque as derived from the generator torque is compared to a commanded engine torque value. An engine running flag is set ON when the fuel command is ON and the difference between the actual and commanded engine torques is less than a predetermined value.
One advantage of the invention is that the vehicle system controller has a reliable indication that the engine has started and is running before torque requests are made of the engine.